GB926292A - Shielding material and process for the production thereof from borates of lead, calcium, barium, magnesium, cadmium or zinc - Google Patents

Abstract

A self-bonding water-insoluble gel is formed by reacting borax with a soluble salt of lead, calcium, barium, magnesium, cadmium or zinc or mixtures thereof at 60-210 DEG F., the solution containing on an oxide bases 1-2 mols of B2O3 per mol of lead or divalent metal oxide. The gel formation may be effected in the presence of, or the formed gel may be mixed with, a reinforcing fibre generally in amounts up to 30% by weight, consisting of asbestos, glass, mineral wool or organic fibres such as cellulose, animal, vegetable or synthetic fibres. The product so formed may be employed as a shielding material against noxious radiations. The filtration time of the borate gel precipitate is decreased and the density of the product increased by adding a boron-containing filler such as colemanite or ulexite which may have been precalcined at 1100-1400 DEG C. Further radiation attenuating material may include metallic lead or iron or compounds thereof. Such fillers are normally used in amounts up to 70% by weight of the total. The dried borate products may be calcined at temperatures up to 1000 DEG F., before use, to remove bound water. According to a typical example borax was dissolved in water at 140 DEG F. and asbestos fibres added thereto, the temperature being maintained at 120 DEG F. Room temperature calcium chloride solution was then added after which mineral colemanite pre-fired at 1350 DEG F. was added and the gel fibre suspension mixed until uniform. The prepared slurry was moulded into blocks by pressing between screens. Further examples relate to similar preparations containing fibres and magnesium, calcium, barium, zinc, cadmium and lead borates. The salt of lead or divalent metal may be of a mineral acid such as nitric acid or an organic acid such as acetic acid.ALSO:A self-bonding water-insoluble gel is formed by reacting borax with a soluble salt of lead, calcium, barium, magnesium, cadmium or zinc or mixtures thereof at 60-210 DEG F, the solution containing on an oxide basis 1-2 mols of B2O3 per mol of lead or divalent metal oxide. The gel formation may be effected in the presence of, or the formed gel may be mixed with, a reinforcing fibre, generally in amounts up to 30% by weight, consisting of asbestos, glass, mineral wool or organic fibres such as cellulose, animal, vegetable or synthetic fibres. The product so formed may be employed as a shielding material against noxious radiations. The filtration time of the borate gel precipitate is decreased and the density of the product increased by adding a boron-containing filler such as colemanite or ulexite which may have been pre-calcined by 1100-1400 DEG C. Further radiation attenuating material may include metallic lead or iron or compounds thereof. Such fillers are normally used in amounts up to 70% by weight of the total. The dried borate products may be calcined at temperatures up to 1000 DEG F, before use, to remove bound water. According to a typical example borax was dissolved in water at 140 DEG F and asbestos fibres added thereto, the temperature being maintained at 120 DEG F. Room temperature calcium chloride solution was then added after which mineral colemanite pre-fired at 1350 DEG F was added and the gel fibre suspension mixed until uniform. The prepared slurry was moulded into blocks by pressing between screens. Further examples relate to similar preparations containing fibres and magnesium, calcium, barium, zinc, cadmium and lead borates. The salt of lead or divalent metal may be of a mineral acid such as nitric acid or an organic acid such as acetic acid.